This invention generally relates to downhole well jarring apparatus as utilized in the drilling and related operations for oil and gas wells. More specifically, the invention pertains to an advance in well jars of the mechanical type as exemplified by the tools disclosed in the prior art.
Well jar apparatus is generally provided of the mechanical type as herein disclosed and of the hydraulic type as well.
The principal disadvantage of the hydraulic type well jars is that they become overheated with continuous use and become either ineffective or inoperative due to the heat. On the other hand, most of the mechanical type jars are difficult to field adjust, if adjustable, to provide a designated jar impact force. Also, the latching or triggering mechanisms in mechanical jars, such as spherical balls for example, are subject to very rigorous wear and deformation forces. Such forces limit the useful term of these mechanical jars until rebuild or replacement.
The presently known prior art are the following: Beck U.S. Pat. No. 1,989,906, Philips U.S. Pat. No. 2,122,751, Kennedy et al U.S. Pat. No. 2,166,299, Howard U.S. Pat. No. 2,634,102, Andrews U.S. Pat No. 2,882,018, Anderson U.S. Pat No. 3,880,249, and Taylor U.S. Pat. No. 4,333,542.